Congratulations!
Normally the visit day is for you to get to know the school and program much better, and for professors and grad students to get to know you.
You will be told information about the classes required for the program, graduation requirements, funding, housing. You will get the chance to talk to the grad students and ask them questions.
Then usually you will have one on one or group discussions with the professors. They will ask you about your research and you can ask them any questions you want. It's best to do thorough research on the professors' research and CV.
And, I almost forgot, in the in-person ones, you would normally be given a tour of the campus. Don't think that will happen during the virtual visitation day